The present invention relates to a technique for preventing a creaking noise produced between a foamed urethane and a metallic surface when the foamed urethane touches on the metallic surface. In particular, the present invention relates to a noise inhibitor and a method for preventing a creaking noise produced between a foamed urethane and a metallic surface when an oil component sticks to the metallic surface and the foamed urethane touches on the metallic surface, and the metallic surface is treated using the noise inhibitor, and thereby, such a creaking noise production is inhibited.
A foamed urethane material has an excellent property as a cushion material and is thus broadly used for a variety of applications. Such foamed urethane products or parts are used alone or together with metallic frames or plates of, for example, a seat or a bed.
However, as a property of a foamed urethane, the foamed urethane product or part is not smoothly moved on a metallic surface, and thus, a creaking noise is disadvantageously produced when the foamed urethane moves on a metallic surface.
When the foamed urethane is used as a cushion material for a seat of an automobile and the like or a mat of abed, such a creaking noise disturbs its comfortable use. Thus, it is required to prevent or inhibit such a noise production.
In the art, in order to prevent such a noise production, a pad such as a non-woven cloth or a felt cloth is attached on a molded foamed urethane product or part so as not to directly touch the foamed urethane to the metallic surface.
A seat used for an automobile is often manufactured by foaming an urethane material in a mold, and a non-woven cloth is placed in a mold before the molding process so as to attach the non-woven cloth on the molded foamed urethane product or part by foaming and molding the foamable urethane material together with the non-woven cloth, in order to prevent the noise production described above.
The noise production can be prevented if such a non-woven cloth is attached on a foamed urethane. However, the number of the manufacturing process is disadvantageously increased, and the whole manufacturing cost is also increased.
The creaking noise produced between the foamed urethane and the metallic surface depends on the metallic surface condition. For example, the creaking noise is not produced very much if the metallic surface is coated with a coating material consisting of melamine alkyd and the like. However, as a recent tendency of an automobile manufacture, in order to reduce the manufacturing cost, it is abolished to use such a coating material for most of metallic frames excepting a particular metallic frame. Thus, the creaking noise production must be prevented by use of a pad such as a non-woven cloth and a felt cloth, and use of such a pad is disadvantageously very expensive as described above.
Meanwhile, the creaking noise production can be prevented by use of grease or Vaseline instead of use of a non-woven cloth or a felt cloth. Grease or Vaseline is applied to a touching area between the foamed urethane and the metallic surface. It seems that the creaking noise production can be prevented by use of grease because grease does not dry in a short time. However, the foamed urethane and the metallic surface are greasy for a long time, and not only its handling is difficult but also other parts and an installed assembling line are contaminated. Thus, it is substantially difficult to use grease or Vaseline in a manufacturing site.
Recently, xe2x80x9ca noise-preventing agent (or a sliding agent)xe2x80x9d coated on the foamed urethane is commercially available. However, it is very expensive and a large quantity of the noise-preventing agent must be coated on the foamed urethane in order to achieve a desired effect. In addition to this matter, as well as grease and Vaseline described above, this agent does not dry in a short time, and other parts and an installed assembling line are contaminated. If the agent is completely dried up to avoid this problem, the noise-preventing effect will not be expected. Thus, use of such a noise-preventing agent is limited.
The present invention is made in order to solve those problems, and therefore, an object of the present invention is to provide a noise inhibitor and a method for preventing a creaking noise produced between a foamed urethane and a metallic surface when an oil component sticks to the metallic surface and the foamed urethane touches on the metallic surface.
Another object of the present invention is to provide a noise inhibitor and a method for preventing such a noise without reducing a rust preventing effect even though the oil component of a rust preventing oil sticks to the metallic surface.
Still another object of the present invention is to provide a noise inhibitor and a method capable of preventing such a noise production even though the treated surface is not only in a wet condition but also in a dry condition.
A noise inhibitor according to the present invention consists of:
a non-ionic or a carboxylic acid type negative ionic oil-soluble surfactant, or a mixture of this oil-soluble surfactant and a water-soluble surfactant; and
water, or a water solution of a wax emulsion solution diluted by 1 to 10 times with water, added thereto such that the oil-soluble surfactant is diluted by 2 to 15 times, desirably 5 to 10 times, with the water or the water solution and the range of pH of the noise inhibitor is from 7.5 to 9.5.
If the surfactant is diluted by 2 to 15 times, the resulting solution (i.e. the noise inhibitor) can be easily coated on a metallic surface and at least more than 10% of the surfactant as a solute dissolves in water or the water-solution.
If the range of pH of the noise inhibitor is from 7.5 to 9.5, the resulting noise inhibitor will be excellent in the stability, the coating ability (in particular, by use of spray), the workability and the rust preventing ability. If the range of pH is below 7.5 (i.e. acidity), the anticorrosion will be reduced. Meanwhile, if the range of pH is above 9.5 (i.e. alkalinity), the anticorrosion will be good but the solution stability becomes worse.
Note that the range of HLB (Hydrophile-Lipophile Balance) (the relative simultaneous attraction of an emulsifier for two phases of an emulsion system) of each surfactant is from 8.0 to 10, desirably from 7.5 to 9.5.
If the range of HLB is above 10, the noise inhibitor exhibits a high hydrophilic property so as to xe2x80x9crepelxe2x80x9d it even though the noise inhibitor diluted with water is coated on a metallic surface, so that the evenly thin coated film layer is not formed over the metallic surface. In addition to this matter, the noise inhibitor coated does not dry in a short time, and this causes that not only the workability becomes worse but also the creaking noise preventing ability is reduced. Meanwhile, if the range of HLB is below 8, the noise inhibitor has a high lipophilic property, so that several properties such as the drying ability, the workability and the creaking noise preventing ability are good and the anticorrosion is improved, but the solution stability becomes worse and the solution is separated.
The noise inhibitor of the present invention can be coated on a metallic surface to which an oil component of a rust preventing oil and the like sticks, by applying a coating technique appropriately selected from means of spraying, brush-painting, role-coat and the like.
After coating, the oil component is emulsified or gelled and the viscosity thereof is almost vanished. Thus, the non-viscous coated film layer is stably and reliably formed over the metallic surface, and this layer is placed between the foamed urethane and the metallic surface, and thereby, the creaking noise production is prevented.
The noise inhibitor of the present invention has no toxicity to a human body and no stimulation to a skin.
In order to examine a mechanism of a creaking noise produced between a foamed urethane and a metallic surface (steel surface), a variety of tests were carried out. The result is as shown in table 1.
As seen in table 1:
1) a large creaking noise is produced if an oil component of a rust preventing oil or a lubricating oil sticks to a metallic surface;
2) there is no creaking noise if a metallic surface is completely cleaned by use of trichlene;
3) a creaking noise is not produced if a measure of rust is produced on a metallic surface; and
4) a creaking noise is not produced if a metallic surface is coated by printing melamine alkyd.
As a result of this test, the creaking noise is produced between a foamed urethane and a metallic surface when the foamed urethane is pushed and moved on the metallic surface if an oil component such as a rust preventing oil and oils and fats sticks to the metallic surface or the foamed urethane. If the metallic surface is completely degreased so as to observe no contamination of such an oil component and is then coated with silicon oil so as to slip or smoothly move, the creaking noise is not produced.
According to the above descriptions, the inventors of the present invention have found that it can be achieved to prevent the creaking noise production by eliminating the viscosity of an oil component such as a rust preventing oil and oils and fats which sticks to a metallic surface and by allowing to smoothly move a foamed urethane on the metallic surface. Also, it has been found that the viscosity of the oil component can be easily eliminated by treating directly the metallic surface rather than by treating the foamed urethane.
As a technique for eliminating the viscosity of the oil component, it is known to apply a surfactant so as to modify the oil component into a hydrophilic emulsion or gel by absorbing the oil component. Meanwhile, it has been found that when a metallic surface to which an oil component sticks is treated by use of a novel noise inhibitor of the present invention so as to modify the oil component into an emulsion or a gel, a foamed urethane is smoothly moved on the metallic surface.
In addition to this matter, as a result of modifying the oil component into a hydrophilic material, if a large quantity of hydrophilic radical is retained on the metallic surface, a desired ability of an oil component such as a rust preventing oil and a lubricating oil may be degraded. However, it has been found that a good workability is obtained and the effect is improved by retaining a least amount of lipophilic radical required to keep the ability.
In addition to this matter, it has been found that the above effect can be obtained even though the noise inhibitor of the present invention coated on a metallic surface is not only in a wet condition but also in a half dry condition.